The invention relates generally to an electronically commutated DC motor (ECM), particularly one adapted to drive a fan.
Motors of this kind are used, inter alia, to drive miniature fans (cf. EP-A1-0 908 630 and corresponding U.S. Pat. No. 6,013,966, FEHRENBACHER) . For various reasons, it may be desirable to operate such a motor without a Hall generator, i.e. to commutate it with the voltage that is induced, during operation, by the rotor in the stator winding.
One object of the invention is therefore to provide a new electronically commutated motor.
In accordance with the invention, the current in the motor is controlled using a bistable multivibrator whose switching state is controlled via at least one comparator. The comparator is in turn controlled by the voltage that is induced by the permanent-magnet rotor in a winding phase that is currentless at that instant. Because a separate rotor position sensor is eliminated, a motor of this kind has a simple configuration with good efficiency, since the power consumption for a rotor position sensor is eliminated. The invention is therefore particularly advantageous for miniature and subminiature motors in which the power consumption of a rotor position sensor, for example a Hall IC, would greatly reduce the electrical efficiency, and it is highly suitable, for example, for motors in which the electronic components are arranged separately from the actual motor (stator with stator winding, and rotor).
Further details and advantageous developments of the invention are evident from the exemplary embodiment described below and depicted in the drawings, which is in no way to be understood as a limitation of the invention.